The Grey's Anatomy star broke things off with Minka Kelly months ago, but isn't dwelling on the past. A source tells ET that Williams couldn't be happier, despite his custody battle with his estranged wife, Aryn Drake-Lee, who claims he already has a new girlfriend.

Drake-Lee alleges in a court document filed on Monday that Williams has taken their children, Sadie and Maceo, "to the home of his girlfriend, whom they now refer to as 'Mama C,' on numerous occasions" since October 2017, and claims that he took his children and girlfriend to Big Bear for two nights in December. A second source, however, tells ET that Williams and the woman are just friends.

According to Drake-Lee, Williams' actions have broken their custody agreement, which orders that "neither parent will introduce the children to a boyfriend/girlfriend until the relationship has endured at least six months." She has asked that his request for more custody of the children be denied.

Williams, meanwhile, is the "happiest" he's ever been, ET's first source says, noting: "He's so free. He's making the choices he wants for himself and the kids. When Jesse is not working, he is with his kids."

"Jesse tried really hard [to make the marriage work] but eventually had to save himself and make a choice not to provide a bad example of a toxic relationship for [his children]," the source adds.

Williams filed for divorce from Drake-Lee in April 2017. See more on the actor in the video below.